KYIV (Reuters) -- President Viktor Yushchenko has criticized domestic and foreign detractors and said Ukraine needed strong institutions to parry threats to its future prosperity.

Yushchenko, whose standing is at rock bottom as he seeks reelection in January, was marking the 18th anniversary of independence from Soviet rule as Ukraine's most modern warplanes and transport aircraft flew in formation over Kyiv city center.

Speaking in Independence Square, focal point of Orange Revolution rallies that swept him to power in 2004, Yushchenko made no direct reference to Russia despite a recent spat.

He spoke only briefly of foreign policy issues that have generated hostility in the Kremlin -- including a drive to secure NATO membership.

"I choose a strong state, strength, and dignity, to put in their place not only our local feudals but also foreign overlords who want to set down how we should live," Yushchenko said in his 25-minute address. "I choose a full-fledged future for our country in the future of a united Europe."

For the second year running, several thousand servicepeople paraded down Kyiv's main thoroughfare, Khreshchatyk Street, and about three dozen aircraft, fighters, bombers, and large military transports, roared overhead.

Tanks rolled down Khreshchatyk last year but this time were parked by the square for crowds to admire. After his address, the president rode down the street aboard an armored truck.

Russian President Dmitry Medvedev this month accused Yushchenko of anti-Russian policies and said he had given up on any improvement on relations as long as he remained in power.

Yushchenko denied the accusation and invited the Russian president for talks.

Rows Over NATO, Georgia, Gas

Relations have soured over Yushchenko's bid to seek NATO membership, his criticism of Russia's military intervention in Georgia, and Kyiv's insistence that Russia's Black Sea Fleet must leave its base in Ukraine's Crimea peninsula by 2017.

The neighbors have also been at odds over gas supplies and prices.

Yushchenko has little chance of reelection as his ratings have hit single figures after nearly five years of infghting.

He trails former Prime Minister Viktor Yanukovych, the Moscow-backed candidate who was initially declared the winner of the 2004 presidential election but lost a re-run after the courts struck down the result as rigged.

Lying second is current prime minister Yulia Tymoshenko, the president's estranged ally. Yushchenko twice appointed her premier, but the two have sniped constantly as Ukraine slipped into a recession, with gross domestic product plunging 18 percent year-on-year in the second quarter.

Tymoshenko has been more moderate in her comments on Russia. Both politicians have pledged to seek better ties with Moscow.

In Moscow, Russian Prime Minister Vladimir Putin sent best wishes on the anniversary to Tymoshenko.

In an oblique reference to the election, Putin hoped the two governments would "contribute to solving practical tasks of cooperation and create a favorable atmosphere for moving forward all aspects of relations between Russia and Ukraine."

Yushchenko has long sought to overturn changes dating from 2004 that cut his power in favor of parliament and the cabinet. Nearly all public figures have proposed some sort of revision.

He said he would sign a decree calling for a countrywide discussion of constitutional changes he has already proposed to settle rows between the president, government and parliament.